James W. Queen Inclination Compass
Figure 1: James W. Queen Inclination Compass. Front corner view.
Figure 2: James W. Queen Inclination Compass. Front center view.
Figure 3: Close view of the label titled "James W. Queen Co, Philadelphia"
This is a dip circle, sometimes referred to as an inclination compass, and is a device for measuring the angle between the horizon and the magnetic field of Earth (the "dip angle"). Because the dip angle varies by latitude (though it does not vary uniformly), it is possible to use a dip circle and a chart of dip angles at different points on Earth to determine one's latitude, albeit with somewhat poor precision. Though a basic dip circle is essentially just a vertically mounted magnetic compass, this instrument also includes a set of precise levelling screws, though one would need to provide a spirit level (which this dip circle lacks) for these screws to be of much use.
In display at KU's Department of Physics & Astronomy building: Malott Hall.